my heater blows cold air

What is your question?

i bought the car it has 226,876 miles and the car runs very good. but the heater does not blow very warm air. and while sittin still the temp hand will raise and the heat gets better. but as soon as you go down the road the heat go back to cold basicly. i have checked the oil and the coolant there is no aparent mixture of either. but there is no loss of either. i thought that maybe the thermostst has been removed but i havent checked. what could be my problem